Marie Curie Initial Training Network

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Johannes Girstmar

My project aims at better understanding the evolution of the animal body plan with focus on the comparative developmental biology of the marine polyclad flatworm Maritigrella crozieri.

It possesses a ciliated planktotrophic larval stage known as Müller’s larva, which shares some morphological similarities to spiralian’s trochophore larvae of annelids and molluscs and to the deuterostome’s larvae of hemichordates and echinoderms.

Despite these observed similarities, the question whether these larvae represent an ancient feature or whether they are a case of convergent evolution is still unresolved.

polyclads are the only group within the Platyhelminthes that undergo indirect development and it has been argued that the existence of a larva in a single order of platyhelminthes points to its convergent evolution in polyclads rather than repeated loss in the other clades but the basal position of the polyclads within Platyhelminthes allows for it to be considered as a primitive character.

Further suggesting that polyclads may have retained ancestral features of their taxa is the fact that their embryonic development shows the stereotypic spiral cleavage pattern with quartets and remarkable similarities to that of other spiralian embryos.

Major goal of this project is to examine in details a number of complex larval structure and developmental processes in order to assess the homology or non-homology of different larval types within Spiralia and Bilateria.

My interest in flatworms stems from two main aspects of their biology: their unique pluripotent stem cell system that give them powerful regeneration capabilities, and their interesting phylogenetic position within the metazoans, which remains a controversial topic.

Working on flatworms during my master’s program (University of Innsbruck) allowed me to gain a first insight into the complexity of flatworm related evo-devo questions. While working on their regeneration, I was able to use confocal laser microscopy for the first time and since then have developed a particular interest in it. Consequently, I am pleased that live imaging techniques such as Light Sheet Fluorescence Microscopy have quickly become a major part of my PhD research project. To me it is exciting to try and establish these new live imaging technologies in polyclad flatworms and trying to combine them with the latest available gene knockout strategies.

I believe that learning to handle these new powerful tools and address them to evo-devo questions is a great opportunity for me, and something I would like to focus on in my future research career.